Spacer having a variable axial length

ABSTRACT

A space keeper for insertion between two vertebrae which has a variable axial length is provided. The space keeper possesses a sleeve-like first member ( 2 ) and a second member ( 3 ) guided in the latter and movable relative to the first member in the axial direction for adjusting an overall length. In order that adjustability during operating is facilitated the two members ( 2, 3 ) are connected to one another by a lever ( 7, 8 ), wherein one centre of motion ( 16 ) of the lever is connected to one member ( 3 ) and the other centre of motion ( 18 ) is connected in terms of action to the other member ( 2 ).

[0001] The invention relates to a space keeper for inserting between twovertebrae, the space keeper having an adjustable axial length and asleeve-like first member and a second member guided in the latter andmovable in the axial direction relative to the first member for settingan overall length.

[0002] A space keeper of this type is known from EP 0 977 528 A1. Inthis the two members in the telescoped position are inserted between twovertebrae and then pulled apart by hand to the desired length and thenlocked in the extended position.

[0003] It is the object of the invention to provide a space keeper ofthe type described at the outset in which the operating surgeon canmanage the adjustment to the desired length in the most simple manner.

[0004] This task is solved by a space keeper of the type described atthe outset which is characterised in that the two members are connectedto one another by a lever one of whose centres of motion is connected toone member and whose other centre of motion is connected to the othermember.

[0005] Refinements of the invention are identified in the subsidiaryclaims.

[0006] Further features and functions of the invention emerge from thedescription of embodiments with reference to the figures. In thefigures:

[0007]FIG. 1 a side view of the space keeper in the contracted position;

[0008]FIG. 2 a section along the line II/II in FIG. 1;

[0009]FIG. 3 the same section as in FIG. 2 but this time with the spacekeeper pulled apart to its maximum length;

[0010]FIG. 4 a plan view onto the object shown in FIG. 1;

[0011]FIG. 5 a second embodiment in the extended position correspondingto the sectional illustration II/II;

[0012]FIG. 6 the second embodiment in the contracted position;

[0013]FIG. 7 a section through another embodiment.

[0014] As may be seen best in FIG. 1 a space keeper 1 comprises asleeve-like first member 2 and a sleeve-like second member 3 guided inthe former. The two members can be pushed into one another to a maximumextent as shown in FIGS. 1 and 2 and be moved apart to a maximum lengthas shown in FIG. 3.

[0015] As may be seen in FIGS. 1 to 3 the inner second member 3 has onits outer wall facing towards the outer first member 2 a section with acatch 4 extending in the axial direction having a plurality ofdepressions 5 arranged adjacent to one another in the axial directionand bounding one another and the outer first member 2 has a fixingmember 6 which can be brought into engagement with the catch. The fixingmember serves the purpose of locking the two members in a desiredposition.

[0016] As may be seen best in FIGS. 2 and 4 the spacer 1 has a leverdevice for adjusting the axial position of the two members relative toone another. In the first embodiment this comprises a first lever arm 7,a second lever arm 8, a setting screw 9 and a threaded sleeve 10. As maybe seen best in FIG. 2 the outer first member 2 has a recess 11 on theside whose lateral extension is smaller than the diameter of the head 12of the setting screw 9 as may be seen best in FIG. 1. The setting screw9 is inserted in the manner shown in FIG. 2 into the interior of thesleeve-like members at right angles to the axial direction. The threadedsleeve 10 is screwed onto the screw. On both sides extending in theaxial direction of the sleeve it has shoulders 13, 14. The shoulder 13serves to connect to the first lever arm 7. The lever arm is mountedpivotably about a shaft 16 by its first end 15 by means of this shaftmounted on two opposite points of the wall of the second member 3. Theshaft extends perpendicular to the longitudinal axis of the spacekeeper. At its second end 17 opposite the connection to the shaft 16 thefirst lever arm is connected pivotably about a shaft 18 to the shoulder13 via a pin or shaft 18. The pin or shaft 18 extends parallel to theshaft 16.

[0017] As illustrated in FIG. 2 the second lever arm 8 viewed about thesetting screw 9 is constructed or arranged symmetrically relative to thefirst lever arm 7. At its first end 19 correspondingly located oppositeend 15 the lever arm is mounted via a shaft 20 to pivot about thelatter. The shaft 20 is mounted on the side in the side walls locatedopposite one another of the first member 2 and extends parallel to theshaft 16. At its end located opposite the end 19 the second lever arm isconnected pivotably about a shaft 21 to the shoulder 14 by means of apin or shaft 21.

[0018] As may be seen in FIGS. 1 and 2 the recess 11 is constructed asan oblong hole extending in a direction parallel to the longitudinalaxis of the spacer. The oblong hole is positioned in such a way that thesetting screw 9 is movable back and forth therein to such an extent thatthe screw is movable back and forth in the oblong hole from thecompressed position shown in FIG. 2 to the extended position shown inFIG. 3.

[0019] In operation the space keeper in the contracted position shown inFIG. 2 with minimal length in the axial direction is inserted betweenthe vertebrae. The length is then set to a desired length by engaging bymeans of a screwdriver in a corresponding slit or hexagonal opening ofthe head 12 of the setting screw 9 in that the setting screw 9 is turnedin such a way that the threaded sleeve 10 is moved from the most extremeposition shown in FIG. 2, in which the threaded sleeve is located at thefree end of the setting screw 9, towards the head. In doing so the twolevers 7, 8 are moved from their retracted position into a maximumextended position shown in FIG. 3. In this way the two sleeve-likemembers 2 and 3 are moved from the contracted position shown in FIG. 2into the expanded position shown in FIG. 3 or any intermediate position.Due to the screw guidance between the setting screw 9 and threadedsleeve 10 the two members remain initially in the position reached byturning the setting screw 9. As soon as this position is regarded asfinal complete locking ensues by tightening the locking screw formingthe fixing member 6 which for this purpose engages in a depression 5 ofthe catch 4.

[0020] In the embodiment described above the length of the setting screw9 is chosen so that the setting screw reaches by its free end into thehollow interior of the second member 3 without coming into engagementwith the opposite wall of the second member 3 so that there is nohindrance to the movement of the second member 3. As shown in thefigures the second member 3 preferably has a recess 22 constructed inthe form of an oblong hole which extends in its longitudinal directionparallel to the longitudinal axis of the space keeper and whose lengthand width are so constructed that the free end of the setting screw 9with the threaded sleeve sliding thereon and the two shoulders 13 and 14and the ends of the two lever arms 7 and 8 connected thereto in theback-and-forth movement shown in FIGS. 2 and 3 can move freely back andforth in the oblong hole. In this way it is achieved that the settingscrew 9 may have a greater length by which means the travel of thethreaded sleeve 10 is increased and hence the expandability of the twomembers or the space keeper is increased.

[0021] In a modified embodiment shown in FIGS. 5 and 6 the second member3, the setting screw 9, the first lever arm 7, the shoulder 13 and thetwo shafts 16 and 18 are constructed in the same way as thecorresponding elements in the first embodiment.

[0022] In the second embodiment, instead of the oblong hole 11 a roundhole 23 guiding the setting screw in the wall of the first member 2′ isprovided whose diameter is chosen so that the setting screw is guidedrotatably in this hole. The threaded sleeve 10′ has only one shoulder13.

[0023] In operation adjustment between the compressed position shown inFIG. 6 and the expanded position shown in FIG. 5 is done as in the firstembodiment by turning the setting screw 9 in such a way that thethreaded sleeve 10′ is screwed so far out of the most extreme positionat the free end shown in FIG. 6 towards the head until expansion to adesired size has occurred or the lever 7 has moved almost into thevertical position. The concluding locking is done as in the firstembodiment by tightening a fixing screw 6 in cooperation with thedepressions 5 of the catch 4.

[0024] As may be seen in the figures the two walls of the first andsecond members are each constructed in such a way that they exhibit inthe circumferential direction a plurality of diamond-shaped apertures24. The free ends 25, 26 located opposite one another are as shown inthe figures each of serrated construction whereby engagement in theadjoining vertebrae walls stabilizing against rotation is facilitated.The apertures in the wall facilitate ingrowing after the operation.

[0025] In the embodiments described above the adjusting device of thesetting screw 9, threaded sleeve 10 and lever arms 7, 8 or 7 isconstructed in each case in such a way that the maximum extension occurswhen the threaded sleeve 10 is moved to the maximum towards the head 12and compressed to the furthest possible when the threaded sleeve 10 isat its greatest possible distance from the head 12. It is also possible,however, to reverse this device to the effect that the greatestextension possible is reached when the threaded sleeve 10 is at itsgreatest distance from the head 12. At the smallest distance from thehead 12 the height has its lowest possible value. Such an embodiment isdescribed in FIG. 7.

1. Space keeper (1) for insertion between two vertebrae which has avariable axial length with a sleeve-like first member (2) and a secondmember (3) guided in the latter and movable relative to the first member(2) in the axial direction for adjusting an overall length,characterised in that the two members (2, 3) are connected to oneanother by a lever (7, 8) one of whose centres of motion (16) isconnected to one member (3) and whose other centre of motion (18) isconnected in terms of action to the other member (2).
 2. Space keeperaccording to claim 1, characterised in that the lever (7, 8) is ofdouble-arm construction, wherein the two ends remote from the centres ofmotion (16, 20) are connected to a threaded sleeve (10) guided on asetting screw (9) guided in an oblong hole (11) of the wall of the firstmember (2).
 3. Space keeper according to claim 1, characterised in thatthe other centre of motion (18) is connected to a threaded sleeve (10′)guided on a setting screw guided in a bore (23) of the wall of the firstmember (2).
 4. Space keeper according to one of claims 1 to 3,characterised in that on the side located opposite the hole (11, 23) thewall of the second member (3) has a longitudinal recess extending in itslongitudinal direction parallel to the longitudinal axis of the spacekeeper into which recess the free end of the setting screw (9) freelyprojects.
 5. Space keeper according to one of claims 1 to 4,characterised in that the second member (3) on its outer wall facingtowards the first member (2) has a section extending in the axialdirection with a catch (4) having a plurality of depressions (5)arranged adjacent to one another in the axial direction and bounding oneanother and the first member (2) has a fixing part (6) acting togetherwith the catch (4) for locking at a desired length.
 6. Space keeperaccording to one of claims 1 to 4, characterised in that the walls ofthe first and second member (2, 3) have apertures (24) distributed overthe surface for improving ingrowing.